Very cool and very inspiring for me personally. It's gotta feel rewarding when you're finished.
I've JUST started undertaking this task myself. We have a partially unfinished basment room with almost identical dimensions to yours (although without the closet.) There are exposed cinderblock walls like you'd find in most basements on 3 sides and I finished the interior wall last winter by insulating it and adding white paneling (it made a HUGE diff in that room's temp.) The other 3 cinderblock walls were already painted a VERY VERY dark green when we first got the house, but it made the room feel SO much smaller than it actually is and it got depressing when I was working out down there (which is where I keep all our gym equipment.) I just finished repainting it this past weekend. Two coats of waterproofing, two coats of Kilz and two coats of paint.

I went for a lighter, more neutral light green/blue to make it feel more open and to go with the beach/tropical decor I plan on putting down there. I also went with that color because my dad was able to hook me up with a ton of free office carpet squares in that color and I wanted the walls to compliment the carpet. I'm probably going to leave my ceiling beams exposed for the time being, although I' might eventually add a dropdown ceiling later (I figure the carpet and new walls alone should be enough to keep my happy for awhile.) I downloaded some free CAD-like software and already worked on the furniture layout. I've got to accommodate the following:
+Desk for main system; will house the following:
-Main system
-19" CRT
-19" TV
-Satellite receiver
-Old pro-logic receiver and CD changer
+Desk for secondary system:
-Secondary system
-17" CRT
-14" CRT
+Filing cabinet
+Large weight bench
+Weight rack
+Stairmaster
+Heavy bag
+Couch or love seat (eventually)
+Spare full-size refrigerator (eventually)
+Recliner
+Coffee table
I recently took over "storing" an old Runco big screen projector we were retiring at our office. While it's not HDTV it's still pretty cool to be able to watch TV on a 70" wide screen. I'd like to start using it more often to watch movies and sports on. I'm also eventually going to inheirit my parents pool table whenever they move into a new house and I'm planning on putting that in there (and migrating the gym equipment to the storage room we'll be building under our back porch.) Maybe I'll post pics once I'm done with mine too. I know several of my coworkers were considering similar designs on their basment/dungeon.